JERUSALEM (CNN) -- Israeli authorities have arrested six Arabs suspected of trying to build an al Qaeda-linked cell, including one person said to have asked about targeting President Bush's helicopter.

Shin Bet, Israel's security service, said in a news release that a 24-year-old student of Hebrew University in Jerusalem decided in January to try to attack a helicopter of a senior official landing on a helipad and took video of the helipad with a cell phone. Bush used that helipad -- near the dormitories at the university's Givat Ram campus -- during a visit in January, it said.

The student, identified as Muhammad Najam, turned to an Internet forum identified with al Qaeda and asked about the possibility of targeting an aircraft carrying Bush, Shin Bet said.

There was no immediate public statement on Najam's behalf.

Shin Bet said the six people arrested have been indicted on various charges, including membership in a terrorist organization.

The six include two Israeli Arabs and four Palestinians from East Jerusalem, all "suspected of planning to set up an al Qaeda-linked infrastructure," the news release said.

The suspects used the Internet to go to radical Islamic Web sites, including some identified with al Qaeda, it said, adding that the computers of some of those arrested had been used to download instructions for preparing bombs.